Tone signal keyer



TONE SIGNAL KEYER Filed July 15, 1942 INVENTOR Jim/ax Luck A-TTIORNEY Patented F eb. 22, 1944 TONE SIGNAL KEYER James L. Finch, East Rockaway, N.

Radi Delaware 2., asalgnor to o Corporation of America, a corporation of Application July 15, 1942, Serial No. 450,982 Claims. (01. 178-66) This invention relates to keying devices for use in telegraph circuits and more particularly to a tone signal keyer.

When electronic circuits are used for the keying of telegraph signals, it is sometimes difllcult to adjust the marking and spacing currents in double-current signaling or to adjust the values of current through the marking and spacing vindings of a polarized relay so thatthe relay tongue will be neutrally biased for vibrating between its marking and spacing contacts.

Accordingly, it is an object of my invention to provide a simple arrangement for adjusting the bias on a keying circuit to meet the practical requirements for normal operation of a telegraph relay or other responsive device;

It is another object of my invention to provide simple means for adjusting the bias of outgoing telegraph signals so that the marking and spacing elements of unit length may be of the same duration.

It is still another object of my invention to provide an electronic keying system utilizing incoming tone signals for actuating a polarized relay, this system to be provided with an adjustable rheostat whereby the bias on the winding circuits of said relay shall be suitably balanced.

Other objects and advantages of my invention will be made apparent in the description to follow. This description is accompanied by a drawing, thesole figure of which represents in diagrammatic form a circuit arrangement suitable for carrying out my invention.

Referring to the drawing, I show therein input terminals I which are connected to an adjustable attenuator 2 enclosed in a broken line rectangle. The output leads from this attenuator are connected respectively to the control grid in a discharge tube 3 and to ground. The discharge tube 3 is preferably of the pentode type. Its input circuit includes a cathode resistor 4 connected between the cathode and ground; while the control grid is also connected to ground through a grid resistor 5. The tube 3 contains the usual anode, suppressor grid, and screen grid.

Anode potential for the tube 3 is supplied by any suitable direct current source 6. The nega tive terminal of this source is connected to ground and the positive terminal is connected through the primary winding of a transformer l to the anode in tube 3. A resistor t is used to supply proper potential to the screen grid. Alternating potentials on the screen grid are by-passed to ground through capacitor 9. Another bypass condenser ofthe source 8.

A double diode rectifier tube It is used to rectify the energy induced in the secondary of transformer 1. This secondary has its terminals connected to the two anodes in the tube H and also has a mid-tap connected through a resistor l2 to the common cathode of tube ll. Resistor I2 is capacitively by-passed by means of condenser l3. A resistor l4 and potentiometer 25 are seriesconnected across the terminals of source 6 for supplying suitable potentials where they are needed, as will be further explained hereinafter. The cathode of tube H is grounded through resistor ll.

A second pentode discharge tube [5 is suitably connected for control either by rectified energy derived from the double diode l I, or by a manual key 6. The tube I 5 has the usual cathode, anode, and three grids. By means of a single-pole double-throw switch [1, the control of the tube III is in shunt with the terminals l5 may be obtained either in accordance with rectified derivatives from incoming tone-modulated signals, or by means of the key It. In either case a marking signal applies a cut-off bias. When the switch I1 is in the position shown, the rectified signal energy flowing through resistor l2 impresses a negative bias on the control grid of tube l5 and blocks the same. When the switch I Tis thrown to the right, and key I6 is closed, then a negative bias is derived from the potential drop through the cathode resistor l 4.

The output circuit of tube l5 includes the primary winding of a transformer I8 and also a spacing" winding IS on a polarized relay 20. This relay has an accelerating winding 2|, the terminals of which are connected across the secondary of transformer l8. Relay 20 also has a marking winding 22 which is continuously energized by source 6, the energizing circuit including resistor 23, rheostat 24, and resistor I4.- The values of the impedances in this marking winding circuit are suitably determined for holding the tongue of relay 20 against its marking contact whenever tube I5 is blocked; that is, when no current flows in relay windings l9 and 2!.

The potentiometer 25 has three sections, a, b, and c in series with resistor I, all being connected across the terminals of the source 6. Between sections a and b is a tap circuit through a resistor 21 to the spacing contact of relay 20. Between sections 11 and c is another tap circuit through a resistor 28 and through shorting contacts of a jack 32 to the tongue of relay 20. The ohmic value ofithe potentiometer section a is adjustable. The marking contact of relay 2,0 is normally connected to the low potential end of potentiometer section through shorting contacts of a jack 3| and through a resistor 28.

The relay 20 has connected between its tongue and its marking and spacing contacts certain spark reducing impedances which include resistors 29 and capacitors 30. p

The jack 3| may be used for supplying single current output to any utilization device such as a recorder or printer. The jack 32 may likewise be used for supplying double current output to a utilization device such as a repeater relay. No utilization device has been shown in the drawing, but it will be understood that such a device may be controlled by the relay 20 if provided with a plug for insertion in either of the jacks 3| or 32. "Plugging in causes the useful external load to replace the impedance of either the resistor 28 .or the resistor 25. The impedance values of resistors 28 and 26 are, therefore, substantially equivalent to the external load or loads to be inserted. Hence a responsive device may have its cord connection plugged into either jack 3| or jack 32. Furthermore, the jacks may serve two responsive devices simultaneously, if desired.

The operation of my keying circuit will now be described. A keyed tone signal at any suitable volume level determined by the adjustment of the attenuator 2 is impressed on the grid of tube 3. This tube amplifies the signal. The signal is then rectified by the tube so that a voltage appears across the resistor l2 and condenser i 3 while the tone signal persists. Let it be assumed that the tone signal indicates a marking condition. It is utilized, of course, by setting switch |'I to the left. The signal voltage is then impressed between the control grid and cathode of tube I5 and is normally of suflicient value to cut off the plate current in this tube. During a spacing period, when no tone is being received, the voltage between the grid and cathode of tube i5 is zero and current of the order of milliamperes flows in the cathode-anode circuit.

The blocking oi. tube IS in the presence of a received marking signal cuts off any current flow that might otherwise traverse windings I9 and 2| in the relay 20. Current continues to flow, however, through winding 22, which is constantly in circuit between the terminals of source 6. this circuit being established through resistor 23, p0- tentiometer 24, and resistor ll. The adjustment of potentiometer 24 provides a suitable current amplitude and voltage drop through the several impedances of this circuit, including relay cofl 22, so that the tongue of relay 20 will be held to the marking side whenever tube I5 is blocked.

2 The steady magnetization force of winding 22 must, however, be so limited as to be effectively overpowered by the energization of winding i9 when tube I5 is rendered conductive. The connection of the screen grid in tube l5 to the lunction between resistor 23 and potentiometer 24 is such as to supply this screen grid with a suitable operating voltage at all times.

When current flows through the tube 55, then the coil I 9 in relay 2!! is energized and causes the tongue of this relay to be moved to the spacing side. The tongue movement is accelerated by a surge impulse inducedin the secondary of transformer l8 and fed through relay coil 2! in aiding relation to the magnetizing force of coil H. Another surge impulse of opposite polarity is induced in the secondary of transformer l8 each time that tube l5 becomes blocked. Hence the relay tongue is reversibly accelerated by currents flowing through coil 2|.

As previously stated. the balance or "bias of the relay 20 is adjusted by means of the rheostat 24. When the impedance of this rheostat 24 is set at its highest value, a relatively low current flows through the relay coil 22. Furthermore, the potential drop across the rheostat is relatively high so that the voltage on the screen grid of tube I5 is raised and causes a relatively high plate current to flow through relay coil |9. When the resistance of rheostat 24 is reduced, this causes more current to flow through the relay coil 20, and at the same time decreases the voltage on the screen grid of tube l5 and causes less current to flow in relay coil l9. Thus a suitable balance can be obtained readily by means of the single control of rheostat 24.- This balance is necessary in order to obtain proper bias in the relay keying action.

The jacks 3| and 32 are arranged for altemative or simultaneous use. When jack 3| holds a plug having conductors to a utilization device, only the marking contact of the relay 20 is used in cooperation with the relay tongue. Marking impulses are thus impressed upon the utilization device by a circuit which may be traced from source 6 through sections a and b of potentiometer 25, resistor 26, the shorting contacts of jack 32, the tongue of relay 20, the marking contact of this relay. the utilization device fed by a plug in jack 3|, resistor l4, and thence to ground. When the tongue of relay 20 is held on the spacing contact, then resistors 26 and '21. are placed in shunt with section b of potentiometer 25, but no current flows to the utilization device.

When the cord plug leading to a utilization device is plugged into jack 32, it is to be presumed that this device requires a reversible current for its operation. Under such conditions one conductor extends to the utilization device from the junction between sections b and c on potentiometer 25 through the sleeve of a plug inserted in jack 32. The tip of this plug then connects directly to the tongue in relay 20 and receives a potential which is positive or negative with respect to the plug sleeve, depending upon the position of the relay tongue.

When the relay tongue contacts on the marking side, its voltage is that which corresponds with the potential drop through resistor 28 to the low potential end of section 0 in potentiometer 25. This voltage drop added to the potential drop through the utilization device equals the voltage drop through section 0 of the potentiometer 25. The utilization device, therefore, receives a potential which is negative with respect to the plug sleeve. When the relay tongue is on the spacing side then its voltage is derived from the more positive junction between sections a and b on potentiometer 25, reduced by the incident potential drop through resistor 21. In this case, therefore, resistor 2'! and the resistance of the utilization device are efiectively in shunt with section b of the potentiometer 25. Hence, the potential drop through the utilization device is positive with respect to the plug sleeve.

When it is desired to change the keying control from tone signals to the manual key i6, switch I?! is thrown to the right. One contact of key It is connected to the'cathode of tube l5 through a resistor 33. The other key contact is grounded. With the key it open, tube i5 is rendered-conductive because its control grid is sustained at cathode potential, since the input circuit includes blocks the tube.

- anode, and a. plurality of switch l1 and the grid resistor 33. The cathode potential is normally above ground potential, due to the constant voltage drop through resistor l4. When the key is closed, however, the grid of tube I 5 is negatively biased to ground potential and this negative bias with respect to the cathode Thus the relay is thrown to the marking position. By opening the key I6, tube I5 is again rendered conductive and the consequent flow of current through coil I9 moves the relay tongue to the spacing side.

While I have described one preferred embodiment of my invention, it will be understood by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. The scope of the claims, therefore, is in-no way limited to the precise details of construction herein shown and described.

I claim:

1. An electronic telegraph keying circuit com prising a discharge tube having a cathode, an grids, including a screen grid, a direct current source supplying operating potentials to the electrodes of said tube, an adjustable potentiometer connected across the terminals of said source, a polarized relay having an operating coil and an opposing bias coil, said operating coil being connected in series with the space path of said tube, and said bias coil being connected in series with at least a portion of stantially one half the amplitude of the current which traverses said one coil in series with the space path of said tube, and causing said potentiometer adjustment to regulate the transconductance of said tube as a direct function of the potentiometer impedance.

6. Apparatus for utilizing an incoming keyed I and tone-modulated signal to reversibly actuate a polarized relay having operating," biasing." and accelerating" coils, said apparatus'comprising a direct current source, a closed circuit connected across the terminals of said source, said circuit including said biasing coil and an adjustable potentiometer, a pentode discharge tube having an output circuit which includes said operating coil and which is energized by said source, means including a screen grid in said tube and a connection thereto irom the high potential end of said potentiometer, whereby the adjustment of said potentiometer determines thetransconductance of said tube,a circuit for said accelerating coil coupled to said output circuit,

said potentiometer, and means including a connection between said screen grid and a point on said potentiometer whereby the screen grid potential becomes a direct function of the ohmic value of said potentiometer and an inverse function of the amplitude of said bias coil.

2. A keying circuit in accordance with claim 1 and including an accelerating coil on said relay, and a transformer the primary winding of which is connected in circuit with said operating coil and the secondary winding of which is connected in circuit with said accelerating coil, said connections being such that the magnetizing eflect of said accelerating coil is reversible, that is, it aids the operating coil at the commencement of a discharge in said tube, and it aids said bias coil at the termination of a discharge in said tube.

3. A keying circuit in accordance with claim 1, and including signal control means for said tube whereby an interrupted tone-modulated wave is rectified and caused to produce a cut-off bias in the input circuit of said tube, thereby to render said relay operable by its said bias coil.

4. A keying circuit in accordance with claim 1 and including a key-actuated direct current cut-ofi biasing means applied to the input circuit of said tube, thereby to render said tube nonconductive and to de-energize said operating coil on said relay.

5. In a. relay circuit arrangement which inthe current traversing cludes a signal-controlled discharge tube and a potentiometer connected across a direct current source of operating potential, the method of adjusting the magnetization forces applied by opposing coils of a polarized relay so that one coil, when energized, efiectively overpowers the other coil and swings the relay armature to one side, and so that said other coil, continuously ener- 'gized and unopposed, eifectively swings said armature to the other side; said method including the steps of adjusting the impedance value of said potentiometer so that the current traversing the same in series with said "other coil has suband means including a full wave rectifier for causing said tube to be blocked during the reception of said signal, thereby to render said relay responsive initially to a surge impulse through its accelerating coil and responsive thereafter to the holding effect of its biasing coil, said oper ating coil, aided by said accelerating coil being eifective, when said tube becomes unblocked, to overpower the magnetization of said biasing coil.

7. In a keying circuit having electronic means responsive to signals for controlling the relative magnetization effects of different coils on a polarized relay, said relay having a tongue which vibrates between a marking contact and a spacing contact, a source of direct current, a voltage divider connected across the terminals 0! said source, a pair of jacks each having sleeve and tip contacts and a "shorting contact which makes with the tip contact when the jack is idle, a resistor interconnected between the sleeve and shorting contact in each jack, a connection between the sleeve contact 01 one said jack and a point of relatively negative potential on said voltage. divider, a connection from the tip con tact of the same jack to the marking contact of said relay, 9. connection from the tip contact of the other jack to the tongue of said relay, a connection from the spacing contact of said relay to a point of relatively positive potential on said voltage divider, and a connection from the sleeve of said other jack to a point on said voltage divider intermediate said points of relatively negative and positive potential.

8. The combination according to claim '7 and including adjustable means on said voltage divider for determining the amplitude of marking impulses fed to a responsive device through a cord and plug inserted in the first said jack.

9. The combination according to claim 7 and including adjustable means on said voltage divider for determining the amplitude of marking and spacing impulses fed to a responsive device through a cord and plug inserted in the second said jack.

10. In combination, a a main operating coil, an an accelerating coil;

polarized relay having opposing bias coil, and an electronic circuit arand control grid of said tube upon reception of a "marking" signal code element, an output circuit for said tube including a source of operating potential, said main operating coil, a trans:- former primary winding, the discharge path of said tube and a cathode resistor; a circuit including said accelerating coil and a transformer sec:- ondary winding inductively coupled to said primary winding; and adjustable potentiometric means in circuit with said screen grid and with said opposing bias coil whereby the screen grid potential becomes a direct function of the ohmic value of said potentiometric means, and the current traversing said bias coil is an inverse function of said ohmic value.

JAMES L. FINCH. 

